Connecting to a server that doesn't respond.
Run this from a local file to avoid cross-origin code path.

<script>
var req = new XMLHttpRequest;
req.open("GET", "http://127.0.0.1:7", true);
req.send();
req.onerror = function() { document.write("onerror<br>"); }
alert("PASSED if no crash or assertion failure");
</script>
